Re: [SI-LIST] : Upper limit of interplane capacitance

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From: Doug McKean (dmckean@corp.auspex.com)
Date: Fri Jun 09 2000 - 11:00:20 PDT


Ray Anderson wrote:
>
> >
> > I would like to point out that what would be the impedance look like
> >when you looks at it from the center of the two plates viewing from
> >the top? Can you still qualify it as a rectangular wave guide as the
> >wave is spread out in 360 degree other than in one particular
> >direction. Instead of calling it the traditional "characteristic
> >impedance" I would prefer to see it as " driving
> >point impedance". Any comment from any guru ????
> >
> >
> > Michael Chan
>
> Not from a guru, but I'll comment.
>
> In both measurement and simulation our group has been able
> show that the spreading inductance exhibited by a plane
> varies according to the measurement point on the plane.
>
> In particular, you'll find the spreading inductance highest
> at the corners (only 2 escape directions), medium on the plane
> edges (3 escape directions) and minimum at central locations
> (4 escape directions).
>
> These variations in spreading inductance that are a function of
> location will also effect the 'driving point impedance' seen
> at those same points.
>
> Any real gurus care to expound on the details?

I ain't no real guru either, but inductance in the plane should
increase as one moves toward the edge just from an intuitive
point of view. and should just about double at the edge when
compared to the middle. This in fact is the case by some studies
done at Curtis-Straus labs im Mass. Written up in their monthly
newsletter a while back. And if I find it, I will post it.

- Doug McKean

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